两个好用的C++库

最近在学习envoy 的源码，发现里面引用的JSON解析和日志记录的库挺好用的，这里简单记录一下

库源码地址

• gabime /spdlog
• nlohmann /json

简单调用

环境基于wsl的ubuntu22.04环境

库函数安装

sudo apt install libspdlog-dev
sudo apt install nlohmann-json3-dev

spdlog库调用

这里使用cmake管理工程

cmake_minimum_required(VERSION 3.15)

project(cpp_test)

#/usr/lib/x86_64-linux-gnu/cmake
find_package(spdlog REQUIRED)
find_package(FMT REQUIRED)

add_executable(main main.cpp)

target_link_libraries(main spdlog)
target_link_libraries(main fmt::fmt)

测试代码(直接拷贝的例子)

#include "spdlog/spdlog.h"

int main(int argc, char const *argv[])
{
    // change log pattern
    spdlog::set_pattern("[%H:%M:%S %z] [%n] [%^---%L---%$] [thread %t] %v");

    spdlog::info("Welcome to spdlog!");
    spdlog::error("Some error message with arg: {}", 1);

    spdlog::warn("Easy padding in numbers like {:08d}", 12);
    spdlog::critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
    spdlog::info("Support for floats {:03.2f}", 1.23456);
    spdlog::info("Positional args are {1} {0}..", "too", "supported");
    spdlog::info("{:<30}", "left aligned");

    spdlog::set_level(spdlog::level::debug); // Set global log level to debug
    spdlog::debug("This message should be displayed..");

    // Compile time log levels
    // define SPDLOG_ACTIVE_LEVEL to desired level
    SPDLOG_TRACE("Some trace message with param {}", 42);
    SPDLOG_DEBUG("Some debug message");
    return 0;
}

文档地址：https://github.com/gabime/spdlog/wiki/1.-QuickStart

使用还是比较简单的，也能满足90%的日志打印需求

nlohman-json库调用

测试代码(也是直接拷贝的例子)

#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;

int main(int argc, char const *argv[])
{
    json ex1 = json::parse(R"(
    {
        "pi": 3.141,
        "happy": true
    }
    )");

    assert(ex1["pi"] == 3.141);

    json ex2 = R"(
    {
        "pi": 3.141,
        "happy": true
    }
    )"_json;

    assert(ex2["pi"] == 3.141);

    json ex3 = {
        {"happy", true},
        {"pi", 3.141},
    };

    assert(ex3["pi"] == 3.141);

    return 0;
}

文档地址：Overview - JSON for Modern C++ (nlohmann.me)

使用也是非常简单，后面有空对比下几个json解析库的性能